BOCA GRANDE, Fla.  Death and taxes may be life's only certainties, but for folks in this upscale island town, add iguanas. And another tax.

In three decades, the resort community on Florida's Gulf Coast has been overrun by the black, spiny-tailed, nonnative lizards that demolish gardens, nest in attics and weaken beach dunes with burrows.

Last month, Lee County commissioners agreed to create a special tax for Boca Grande to cover costs of studying the infestation on the barrier island of Gasparilla, where scientists estimate there are up to 12,000 iguanas on the loose, more than 10 for every year-round resident.

The frustration here has led to frenzy. Bonnie McGee keeps a pellet gun by her door ready to take on the slithering enemy.

"They eat your flowers and their feces is everywhere," she said, adding that she's killed dozens. "Some people toss them in the canal and the hermit crabs feed on them."

Aaron Diaz, owner of Boca Grande's Barnichol hardware store, said he has sold 75 traps in the past three weeks alone.

"For some people, they've really taken over, climbing into attics, into vents and even into their toilets," he said.

County Commissioner Bob Janes doesn't know how much eradication will cost yet, so he's not sure how much the tax will be. He said the issue has finally come to a head.

"In 1988, there was talk of a program but people at that time thought they were kind of cute," Janes said. "They're no longer cute little guys. They're very pesky. They eat turtle and bird eggs and burrow into sand dunes. We could lose a lot of sand in a storm."

Kevin Enge, an exotic species expert with the Florida Fish and Wildlife Conservation Commission, said he believes the iguana was introduced to Boca Grande in the 1970s by a boat captain who brought a few from Mexico for his kids but released them when they grew too large. Their population exploded because each female iguana can lay up to 75 eggs a year.

The reptiles are found in a few other places in Florida, but nowhere in the numbers seen on Gasparilla Island, home to television renovator Bob Vila and a vacation spot for the Bush clan.

"There's no way you'll get rid of them all. Once they're established to that extent, it's a lost cause," Enge said.

The county hired Florida Gulf Coast University biologist Jerry Jackson to study the problem. He is worried the lizards aren't just a nuisance, but are destroying native habitat, spreading other invasive species through their droppings and endangering the town in the event of a hurricane.

"The majority of their burrows are in the dunes along the beaches," Jackson said. "We're threatening the human population on Gasparilla Island to the extent that the dunes are in danger of just disappearing with a storm surge."

The iguanas feed on the eggs of gopher tortoises, a species of "special concern" that the state says will likely to be bumped up to threatened in a few months as their population declines.

The lizards also carry salmonella.

"The disease organism alone could be a problem for native species, even for humans," Jackson said. "It's a zoo out there. It's an ecosystem gone crazy."

"We need some degree of iguana control here otherwise we're going to be up to our knees in them," said Gary Dutery, editor of the weekly Boca Beacon. His paper gets flooded with letters from residents.

"Iguanas are not human. They do not deserve humane treatment," resident Richard Zellner wrote. "As far as I am concerned, they can be burned, shot and mutilated."

Some have even made catching iguanas into a family outing. Boston resident Michael Mavilia, 49, owns a house on the island, so he spent a recent day with his family casting a fishing rod with a tiny green rubber worm toward the foundations of beach homes.

"This is a nice one," Mavilia said, pulling a writhing, two-foot iguana from a cage in his car trunk. "You should have seen us wrestling him in. It was like catching the big one."